Method of rolling



1 Patented Dec. 25, 1945 METHOD or ROLLING Charles J. Fiscus, Arnold, Pa, assignor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania No lh'awlng. Application April 11,1945,

Serial No. 587,826

2 Claims. (Cl. his-11.5)

This invention relates to improved methods of rolling by which aluminum base alloys containing about 3 to per cent by weight of tin may be satisfactorily fabricated into the form of sheet. Usual methods employed in the rolling .of aluminum base alloy ingot to sheet form comprise three basic steps which are, in order, the hot rolling of ingot .to form slab, the annealing of the slab to remove therefrom strain hardness, and the cold rolling of the annealed slab to sheet of the desired thickness.

When aluminum base alloys containing substantial amounts of tin are subjected to such methods of rolling, using temperatures normally employed in the hot rolling of other aluminum base alloys, these tin-containing alloys do not respond favorably. At temperatures which peratures of over 550 F. has seriously inter fered with the use of these alloys in sheet form.

It is the purpose and object of this invention to provide improved methods of hot rolling by which may be produced aluminum-tin alloy slab which does not excessively liquate when heated to temperatures of 550 to 850 FL The improved must be used for the satisfactory annealing of hot rolled slab, temperatures which are in the order of about 750 F., plus or minus 50, the aluminum-tin alloy slab exudes a. portion'of its tin component to [the slab surface. phenomenon, commonly called liquation, occurs in these aluminum base tin-containing alloys in varying degree and, while this liquation may be tolerated to some extent, any substantial exudation of the tin component of the slab sur-.

face during the annealing step will preclude satisfactory reduction of the slab in the subsequent cold rolling step. The amount of liqua- Thistion of the tin constituent in the slab increases with increases in temperature above about 500 F. An annealing temperature in the range of about 550 to 650 1'. will usually satisfactorily prepare the hot rolled slab for the further cold rolling step. However, special circumstances are encountered from time to time where it is necessary to heat the slab to even higher temperatures preparatory to its finalcold rolling. Thus where a hot rolled slab of aluminum base alloy of the indicated tin content is to be bonded to another slab or sheet prior to cold rolling so that the final product of the cold rolling will be a-duplex or laminated sheet, proper bonding may require the exposure of the aluminum-tin alloy slab to temperatures as high as 850 F. Such temperatures cause excessive liquation of the tin constituent of the alloy. The aluminum base alloys containing 3 to 10 per cent by weight of tin are very useful in the form of sheet as bearing alloys and are likewise useful as a component of duplex or laminated sheet for the same purpose, but the excessive liquation encountered when the hot rolled slab is heated to temmethod of this invention will not entirely prevent exudation of the tin constituent on the slab surface when the slab is heated to those temperatures, but the exudation will be so reduced as to allow the commercial fabrication of cold rolled sheets of these tin-containing aluminum base alloys. This result will be obtained. in

' accordance with this invention, if the hot rolling step is preceded by a preliminary heat treatment of the' ingot for a length of time of about 1 to 12 hours within a temperature range of about 575 to 660 F., and if subsequent hot rolling is then carried out at temperatures of about 300 to 450 F. Ingot to which reference is made herein may be in the usual form of cast ingot such as is used insheet rolling, or the work piece may .be a suitably sized billet prepared by a preliminary working step such as forging or extrusion. In

any event, this ingot or billet of aluminum-tin alloy is preheated at 570 to 660 F. for a time of between about 1 to 12 hours preliminary to the hot rolling operation. Thereafter the ingot or billet may be cooled to the rolling temperature or it may be allowed to cool to a lower temperature or to room temperature and later be heated to the rolling temperature, whichever- .then prevailing. However, the hot rolling step in which the preheated ingot or billet is reduced to slab is, inaccordance with this invention, conducted at metal temperatures in the range of about 300 to 450 F. If this combination of preheating and 'hot rolling is followed, the resultant slab may then be exposed to annealing temperatures of 550 to 850 13'. without causing excessive liquation of the tin constituent. While the practice of this improved method of rolling will not usually produce a slab which will not liquate at annealing temperatures, the slabs so produced will not exhibit such excessive liquation as to prevent commercial and practical rolling of the annealed slab into sheet form.

The aluminum base alloys containing 3 to 10 per cent byweight of tin to which reference is conveniently added to-h'arden or strengthen or otherwise improve or modify the properties of the alloy. Slab is used herein as a term of art denoting a rolled product which has undergone from ingot form a reduction of about 50 to 90 per cent, which reduction usually, but not necessarily, results in a rolled product having the thickness ofabout 0.25 to 0.5 inch.

As an example of the specific application of the improved methods of this invention, may be cited the rolling of an ingot of an alloy consisting of about 6.5 per cent by weight of tin, 1 per cent by weight of nickel, and 1 per cent by weight of copper, the balance being aluminum with some impurities. This ingot was preheated at 600 F. for four hours and was then hot rolled at temperatures of 400 to 450 F. until the total reduction was 70 per cent, the resultant slab being about 0.25 inch in thickness. Samples of this slab annealed at temperatures of 650 and 800 F. exhibited some exudation of tin constituent on the slab surface but not in suflicient amount to said ingot or billet for a period of about 1 to 12 hours at temperatures of about 575 to 650 F. and thereafter rolling the thus preheated ingot or billet to slab form at rolling temperatures within the range of about 300 to 450 F.

2. In that method of producing sheet from ingot or billet of aluminum base alloy containing about 3 to 10 per cent by weight of tin, which comprises prevent cold rolling of the annealed slabto produce a satisfactory cold rolled sheet of about 0.08

inch in thickness.

hot rolling the ingot or billet to slab form, annealing the .slab at temperatures of about 550 to 850 F. and thereafter cold rolling the annealed slab to sheet of desired thickness, the improvement which consists in preliminarily subjecting the ingot or billet to temperatures of about 575 to 650 F. for a period of between about 1 to 12 hours and thereafter rolling the thus treated ingot or billet to slab form at rolling temperatures of between about 300 and 450 F.

. CHARLES J. FISCUS. 

